Getting to the Root of Bacterial Hairs: What is “s”?

An atomic force microscope (AFM) was used to measure the steric forces of lipopolysaccharides (LPS) on the biofilm-forming bacteria, Pseudomonas aeruginosa. It is well known that LPS play a vital role in biofilm formation. These forces were characterized with a modified version of the Alexander and de Gennes (AdG) model for polymers, which is a function of equilibrium brush length, L, probe radius, R, temperature, T, separation distance, D, and an indefinite density variable, s. This last parameter was originally distinguished by de Gennes as the root spacing or mesh spacing depending upon the type of polymer adhesion; however since then it has been commonly thought of as the root spacing. This study aims to clarify the ambiguity of this parameter as a first step in characterizing biofilm formation. Varying the temperature and pH at which the steric forces of the LPS are measured and then analyzing the produced force curves with Matlab, should allow us to measure s. The Matlab program has been written to crop large numbers of force curves in accordance with the Alexander and de Gennes polymer model objectively and quickly. If s is the root spacing it should remain constant regardless of the changing polymer lengths, on the other hand if it is the mesh spacing it will be proportional to the temperature and pH. Preliminary data suggest that the LPS vary with temperature and pH. The data also suggest that s represents the mesh spacing. Once s has been described, further studies can be done to determine how environmental changes influence L, and s and consequently biofilm formation

Explosive volcanism in complex impact craters on Mercury and the Moon: influence of tectonic regime on depth of magmatic intrusion

Vents and deposits attributed to explosive volcanism occur within numerous impact craters on both the Moon and Mercury. Given the similarities between the two bodies it is probable that similar processes control this spatial association on both. However, the precise morphology and localization of the activity differs on the two bodies, indicating that the nature of structures beneath impact craters and/or volcanic activity may also be different. To explore this, we analyze sites of explosive volcanism within complex impact craters on the Moon and Mercury, comparing the scale and localization of volcanic activity and evidence for post-formation modification of the host crater. We show that the scale of vents and deposits is consistently greater on Mercury than on the Moon, indicating greater eruption energy, powered by a higher concentration of volatiles. Additionally, while the floors of lunar craters hosting explosive volcanism are commonly fractured, those on Mercury are not. The most probable explanation for these differences is that the state of regional compression acting on Mercury's crust through most of the planet's history results in deeper magma storage beneath craters on Mercury than on the Moon. The probable role of the regional stress regime in dictating the depth of intrusion on Mercury suggests that it may also play a role in the depth of sub-crater intrusion on the Moon and on other planetary bodies. Examples on the Moon (and also on Mars) commonly occur at locations where flexural extension may facilitate shallower intrusion than would be driven by the buoyancy of the magma alone

Omega-3 fatty acids and genome-wide interaction analyses reveal DPP10-pulmonary function association

Rationale: Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have anti-inflammatory properties that could benefit adults with comprised pulmonary health. Objective: To investigate n-3 PUFA associations with spirometric measures of pulmonary function tests (PFTs) and determine underlying genetic susceptibility. Methods: Associations of n-3 PUFA biomarkers (a-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid [DPA], and docosahexaenoic acid [DHA]) were evaluated with PFTs (FEV1, FVC, and FEV1/FVC) in meta-analyses across seven cohorts from the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium (N=16,134 of European or African ancestry). PFT-associated n-3 PUFAs were carried forward to genome-wide interaction analyses in the four largest cohorts (N=11,962) and replicated in one cohort (N=1,687). Cohort-specific results were combined using joint 2 degree-of-freedom (2df) meta-analyses of SNPassociations and their interactions with n-3PUFAs. Results: DPA and DHA were positively associated with FEV1 and FVC (P < 0.025), with evidence for effect modification by smoking and by sex. Genome-wide analyses identified a novel association of rs11693320-an intronic DPP10 SNP-with FVC when incorporating an interaction with DHA, and the finding was replicated (P-2df = 9.4 x 10(-9) across discovery and replication cohorts). The rs11693320-A allele (frequency, similar to 80%) was associated with lower FVC (P-SNP = 2.1 x 10(-9); beta(SNP) = 2161.0 ml), and the association was attenuated by higher DHA levels (P-SNPxDHA interaction = 2.1x10(-7); beta(SNPxDHA interaction) = 36.2 ml). Conclusions: We corroborated beneficial effects of n-3 PUFAs on pulmonary function. By modeling genome-wide n-3 PUFA interactions, we identified a novel DPP10 SNP association with FVC that was not detectable in much larger studies ignoring this interaction

Determining the Parameters of Force Curves on Pseudomonas aeruginosa: Is “s” the Root Spacing or the Mesh Spacing?

Pseudomonas aeruginosa is extremely harmful to immunocompromised individuals. An atomic force microscope was used to measure the surface forces of this bacteria’s exopolymers. These forces were characterized with the AdG force model, which is a function of brush length, probe radius, temperature, separation distance and an indefinite density variable, s. This last parameter could represent the root spacing or mesh spacing of the exopolymers. This study aims to clarify s by obtaining force values as a function of temperature. The data suggest that s represents the mesh spacing. If s is the root spacing it should remain constant regardless of the changing polymer lengths, on the other hand if it is the mesh spacing it will vary with changing temperature, as shown by the data presented in this research. This knowledge will aid in understanding and characterizing how bacteria cause infections

WPI Teaching Practicum

The practicum, or student teaching, was done at Shepherd Hill Regional High School under the supervision of Mrs. Debra Richard. Shepherd Hill is located in Dudley Massachusetts and contains students from both Charlton and Dudley. Mrs. Richard has been employed at Shepherd Hill for many years and is a well-known mathematics teacher. Over the course of seventy-five hours, observation of Mrs. Richard's teaching style and ability was made.Once the seventy-five hours of observation was completed one hundred and fifty hours of student teaching took place

Determining the Parameters of Force Curves on P. aeruginosa

Pseudomonas aeruginosa is very harmful to immunocompromised individuals. An atomic force microscope was used to measure the surface forces of this bacteria's exopolymers. These forces were characterized with a force model, which is a function of brush length, probe radius, temperature, separation distance and an indefinite density variable, s. This last parameter could represent root spacing or mesh spacing of the exopolymers. This study aims to clarify s by obtaining force values as a function temperature. Data show the brush length to be on the scale of several hundred nanometers while s is on the scale of tens of angstroms and is varying with temperature suggesting that s represents the mesh spacing. This knowledge will aid in developing treatment for bacterial infections